1. Field of the Invention
This invention relates to dental handpieces, and more particularly to a swivel for an illuminated dental handpiece which enables the efficient passage of light, air, and water through an easily disconnectable, rotatable connection.
2. Background to the Invention
It has been customary now for some years to provide dental handtools, especially handpieces, with a means of illuminating the operative site. The light is usually transmitted either from a bulb located in the proximal end of the tool (as used in this specification, the term "distal" refers to that end which is closest to the operative site in use, and "proximal" refers to that end remote from the operative site) or from a separate light source unit and then conveyed to the distal end via an optical fiber bundle passing through the handpiece. An example of such an illuminated handpiece is given in Wallace, U.S. Pat. No. 4,341,518.
It has also become popular to provide dental handpieces with a swivel or rotatable connection, so that that part of the handpiece near the distal end and including the part which is held by the operator may freely rotate with respect to the proximal part which is connected to the supply of operating media, such as air, water, light, and/or electric power. The rotatable connection is also preferably easily removable, so that different handpieces may be readily interchanged on the same supply (the term "handpieces" as used in this specification is intended to encompass powered drills (both high- and low-speed), powered scalers, powered endodontic instruments, and the like). Examples of handpieces including such swivels are given in, e.g., U.S. Pat. Nos. 3,936,940 and 4,217,101 to Loge; U.S. Pat No. 4,260,382 to Thomson; U.S. Pat. No. 4,303,392 to Rollofson; and U.S. Pat No. 4,321,039 to Schuss et al.
When it is desired to provide both illumination and a rotatable connection, it is generally considered desirable to route the light path along the central, longitudinal axis of the swivel connectors, at least at the point where the connection occurs, to ensure that the intensity of illumination is unaffected by the rotation. Handpieces illustrating such a light path are described in, e.g., U.S. Pat. Nos. 4,353,697 and 4,403,956 to Nakanishi; U.S. Pat. No. 4,398,885 to Loge et al.; and U.S. Pat. No. 4,431,412 to Lares et al.
Several disadvantages have been found in such handpieces. Because of the plurality of paths for operating media (typically drive air, chip or coolant air, water, light, and exhaust air), the swivel section tends to be longer and/or larger in diameter than is desirable, bearing in mind the balance and "feel" of the handpiece. Additionally, rotation tends to require a high torque because of the number of seals and other frictional contacts between rotating parts, and as the number and length of gaps in the optical path increases, a lower intensity of illumination at the operative site results. Furthermore, such swivels often tend to be complex and expensive.
It would, therefore, be desirable to provide a swivel connector for an illuminated dental handpiece which would overcome one or more of the disadvantages set forth above, and be both inexpensive and easy to use.